The PI will conduct full-3D waveform tomography (F3DT) for the seismic velocity and attenuation structure on the San Andreas Fault zone around the Parkfield area in California. In the F3DT algorithm, both the reference structural model and the derived model perturbations are all 3D in space and the full-wave sensitivity (Fréchet) kernels are calculated from the full physics of 3D wave propagation. Joint inversions will be carried out for both seismic velocity and attenuation structures of the San Andreas Fault Zone using waveform recordings from natural and/or man-made earthquakes. By integrating high-quality waveform data into the F3DT algorithm, they expect to substantially enhance both the resolution and the accuracy of the 3D seismic velocity and attenuation structure in the Parkfield area.
Variations in physical properties of a fault zone may influence the generation, propagation and arrest of large earthquakes. Results from previous studies suggest that inelastic processes such as migration of fluids in fractures or microcracks and the associated changes in pore pressure and chemical effects such as stress corrosion and pressure solution may lead to mechanical failure and nucleation of earthquakes. Since attenuation structure is sensitive to fracturing, crack accumulation and partial saturation, the proposed high-resolution full-3D waveform tomography for fault-zone attenuation structure will provide important additional constraints to improve our understanding of fault-zone processes.
This project is funded jointly by the EPSCoR, Earthscope and Geophysics programs.
Variations in physical properties of a fault zone may influence the generation, propagation and arrest of large earthquakes. Results from previous studies suggest that inelastic processes such as migration of fluids in fractures or microcracks and the associated changes in pore pressure and chemical effects such as stress corrosion and pressure solution may lead to mechanical failure and nucleation of earthquakes. We have developed a new full-3D, full-waveform seismic tomography technique and applied it to the Parkfield region to image the seismic velocity structures in and around the San Andreas Fault. In this new seismic tomography technique, both the reference structural model and the derived model perturbations are all 3D in space and the full-wave sensitivity (Fréchet) kernels are calculated from the full physics of 3D wave propagation, which is implemented using the discontinuous Galerkin method. Our parallelized computer codes can effectively take advantage of modern distributed-memory computer clusters with accelerators and can scale to tens of thousands of processors with excellent strong and weak scaling. This new tomography technique allows us to extract high-resolution images of the subsurface from the details of the seismic waveforms recorded by modern broadband seismometers. It is applicable not only to the Parkfield region, but also to many other regions with passive and/or active seismic sources at a varity of geographic scales.
